Brief History of Sudoku

iPhone application from grreeny.com

The 18th century Swiss mathematician Leonhard Euler developed the concept of Latin Squares where numbers in a grid appear only once, across and up and down. Two hundred years after Euler, in 1979, retired American architect Howard Garns contributed puzzles titled Number Place for publication by Connecticut-based crossword giant Dell Magazines.

In the mid 80s, a Japan company, Nikoli Inc., introduced a version of the puzzle that became a huge hit. "Su" means number in Japanese, and "Doku" refers to the single place.

There are 6,670,903,752,021,072,936,960 possible combinations for completing a 9-by-9 sudoku but it requires no SAT scores and has nothing to do with mathematics but challanges children and adults all over the world. It is a universal game, using plain rules of logic and deduction.

In Sudoku Vario you may choose not only numbers but letters, symbols, and images to play with. Completing the puzzle requires attention, patience and logical ability.

Rules

An iPhone application from Adam Debreczeni

Our task is to fill all the blank cells with the correct numbers. There are three simple constraints to follow:

1. Rows of 9 numbers must include all digits 1 through 9 in any order (see red frame)

2. Columns of 9 numbers must include all digits 1 through 9 in any order (green)

3. Every 3x3 region of the 9x9 game table must include all digits 1 through 9 (yellow)

To solve the puzzle, every row, column and region, each consisting of 9 entries, must include all numbers from 1 to 9. No number is allowed to be duplicated or omitted. Some so called 'given numbers' will already be inserted into the puzzle. The higher number of pre-inserted cells indicates a lower level of difficulty. Solving a Sudoku can take, depending on the difficulty level, between 3 minutes and 2 hours. Be carefully when you set your level of difficulty and countdown timer in Sudoku Vario. :-)